EFFECT OF OSMODEHYDROFREEZING ON THE QUALITY ATTRIBUTES OF FROZEN TOMATO

Vegetable such as tomatoes are not suitable for traditional freezing process, due to texture degradation, color alteration, nutritional loss, high energy costs, etc. Poor quality of these frozen tissues can significantly be improved by means of the cryoprotection accomplished by the pre-osmotic dehydration The objective of this research was to study the effect of osmotic pretreatment with different sweeteners on the quality of frozen Tomatoes at -180C in a circulating air prior to evaluation of quality attributes. The tomato pieces were osmotically dehydrated in Salt (10% w/v) and sugar (25%w/v) solutions at 30oC for 0-5 hrs and packed in polyethylene bags before freezing in air circulating freezer at -18oC; an untreated sample was also used for comparison. The chemical properties of frozen tomato pieces were studied during storage at -18oC after 5 and 30 days. Results showed that vitamin A loss for both osmohydrofrozen and non pretreated samples were not significantly different (p< 0.05); 179.44g/100mg and 181.37g/100mg respectively, while vitamin C, potassium and phosphorus loss were slightly varied. Color of the frozen tomato pieces was acceptable and unaffected by the thawing process. After 30 days of storage, results of sensory evaluation showed that the sample treated with sucrose and salt was more acceptable in terms of texture, color, flavor, aroma, and overall acceptability than untreated sample. Osmodehydrofrozen samples were closer to the color of fresh tomato than samples without pretreatment.